NOTES

This program is mostly obsolete. Replacement for netstat is ss. Replacement for netstat-r is iproute. Replacement for netstat-i is ip-slink. Replacement for netstat-g is
ipmaddr.

DESCRIPTION

Netstat prints information about the Linux networking subsystem. The type of information
printed is controlled by the first argument, as follows:
(none)
By default, netstat displays a list of open sockets. If you don't specify any address
families, then the active sockets of all configured address families will be printed.
--route,-r
Display the kernel routing tables. See the description in route(8) for details. netstat-r and route-e produce the same output.
--groups,-g
Display multicast group membership information for IPv4 and IPv6.
--interfaces,-i
Display a table of all network interfaces.
--masquerade,-M
Display a list of masqueraded connections.
--statistics,-s
Display summary statistics for each protocol.

OPTIONS

--verbose,-v
Tell the user what is going on by being verbose. Especially print some useful information
about unconfigured address families.
--wide,-W
Do not truncate IP addresses by using output as wide as needed. This is optional for now
to not break existing scripts.
--numeric,-n
Show numerical addresses instead of trying to determine symbolic host, port or user names.
--numeric-hosts
shows numerical host addresses but does not affect the resolution of port or user names.
--numeric-ports
shows numerical port numbers but does not affect the resolution of host or user names.
--numeric-users
shows numerical user IDs but does not affect the resolution of host or port names.
--protocol=family, -A
Specifies the address families (perhaps better described as low level protocols) for which
connections are to be shown. family is a comma (',') separated list of address family
keywords like inet, inet6, unix, ipx, ax25, netrom, econet, ddp, and bluetooth. This has
the same effect as using the --inet|-4, --inet6|-6, --unix|-x, --ipx, --ax25, --netrom,
--ddp, and --bluetooth options.
The address family inet (Iv4) includes raw, udp, udplite and tcp protocol sockets.
The address family bluetooth (Iv4) includes l2cap and rfcomm protocol sockets.
-c,--continuous
This will cause netstat to print the selected information every second continuously.
-e,--extend
Display additional information. Use this option twice for maximum detail.
-o,--timers
Include information related to networking timers.
-p,--program
Show the PID and name of the program to which each socket belongs.
-l,--listening
Show only listening sockets. (These are omitted by default.)
-a,--all
Show both listening and non-listening sockets. With the --interfaces option, show
interfaces that are not up
-F
Print routing information from the FIB. (This is the default.)
-C
Print routing information from the route cache.

OUTPUT

ActiveInternetconnections (TCP, UDP, UDPLite, raw)
Proto
The protocol (tcp, udp, udpl, raw) used by the socket.
Recv-Q
Established: The count of bytes not copied by the user program connected to this socket.
Listening: Since Kernel 2.6.18 this column contains the current syn backlog.
Send-Q
Established: The count of bytes not acknowledged by the remote host. Listening: Since
Kernel 2.6.18 this column contains the maximum size of the syn backlog.
LocalAddress
Address and port number of the local end of the socket. Unless the --numeric (-n) option
is specified, the socket address is resolved to its canonical host name (FQDN), and the
port number is translated into the corresponding service name.
ForeignAddress
Address and port number of the remote end of the socket. Analogous to "Local Address".
State
The state of the socket. Since there are no states in raw mode and usually no states used
in UDP and UDPLite, this column may be left blank. Normally this can be one of several
values:
ESTABLISHED
The socket has an established connection.
SYN_SENT
The socket is actively attempting to establish a connection.
SYN_RECV
A connection request has been received from the network.
FIN_WAIT1
The socket is closed, and the connection is shutting down.
FIN_WAIT2
Connection is closed, and the socket is waiting for a shutdown from the remote end.
TIME_WAIT
The socket is waiting after close to handle packets still in the network.
CLOSE The socket is not being used.
CLOSE_WAIT
The remote end has shut down, waiting for the socket to close.
LAST_ACK
The remote end has shut down, and the socket is closed. Waiting for
acknowledgement.
LISTEN The socket is listening for incoming connections. Such sockets are not included in
the output unless you specify the --listening (-l) or --all (-a) option.
CLOSING
Both sockets are shut down but we still don't have all our data sent.
UNKNOWN
The state of the socket is unknown.
User
The username or the user id (UID) of the owner of the socket.
PID/Programname
Slash-separated pair of the process id (PID) and process name of the process that owns the
socket. --program causes this column to be included. You will also need superuser
privileges to see this information on sockets you don't own. This identification
information is not yet available for IPX sockets.
Timer
(this needs to be written)
ActiveUNIXdomainSocketsProto
The protocol (usually unix) used by the socket.
RefCnt
The reference count (i.e. attached processes via this socket).
Flags
The flags displayed is SO_ACCEPTON (displayed as ACC), SO_WAITDATA (W) or SO_NOSPACE (N).
SO_ACCECPTON is used on unconnected sockets if their corresponding processes are waiting
for a connect request. The other flags are not of normal interest.
Type
There are several types of socket access:
SOCK_DGRAM
The socket is used in Datagram (connectionless) mode.
SOCK_STREAM
This is a stream (connection) socket.
SOCK_RAW
The socket is used as a raw socket.
SOCK_RDM
This one serves reliably-delivered messages.
SOCK_SEQPACKET
This is a sequential packet socket.
SOCK_PACKET
Raw interface access socket.
UNKNOWN
Who ever knows what the future will bring us - just fill in here :-)
State
This field will contain one of the following Keywords:
FREE The socket is not allocated
LISTENING
The socket is listening for a connection request. Such sockets are only included
in the output if you specify the --listening (-l) or --all (-a) option.
CONNECTING
The socket is about to establish a connection.
CONNECTED
The socket is connected.
DISCONNECTING
The socket is disconnecting.
(empty)
The socket is not connected to another one.
UNKNOWN
This state should never happen.
PID/Programname
Process ID (PID) and process name of the process that has the socket open. More info
available in ActiveInternetconnections section written above.
Path
This is the path name as which the corresponding processes attached to the socket.
ActiveIPXsockets
(this needs to be done by somebody who knows it)
ActiveNET/ROMsockets
(this needs to be done by somebody who knows it)
ActiveAX.25sockets
(this needs to be done by somebody who knows it)